Electric hub motor improves EV range: Part 1—Technology basics

Part 2 of this feature covers applications at higher, more practical speeds and manufacturability.

Most of the electric cars currently available are using brushless permanent magnet (PM) motors. These motors have very good characteristics, but their control circuitry consumes a lot of power, that may require liquid cooling. This wasted energy is taken from the energy stored in the battery, reducing the range of the car.

For hybrid vehicles using series power train technology (the combustion engine drives an electrical generator charging the battery), this waste of energy translates into a reduction of the miles covered per gallon of gas.

This series describes the concept of a brushless DC motor with an "electronic gearbox," requiring an almost lossless control circuitry. This translates into improved range, which is also increased by a nearly 100% regenerative braking energy recovery, as well as reduced manufacturing cost and better reliability.

The motor described here is designed to fit into the wheels of a 4WD car. The same concept can be used for implementations of a centralized electrical motor with mechanical transmission. Other implementations of the concept can be considered.

Motor and gearbox basics
The axle of the motor is fixed, with no transmission of any mechanical energy from the vehicle to the wheels (which allows for simplified shock absorbers and improvement of the energy transmission yield). The stator of the motor, "tied" to the axle, is made of printed circuits with copper electric wires. The rotor of the motor is made of magnets and is joined to the rim of the wheel, turning around the axle.

The described motor is made up of a dozen “stacks.” Each stack is 5-mm thick, and is made of a disk of magnets, 3-mm thick, and a printed-circuit disk, 1.8-mm thick, with a 0.2-mm gap between the stator and rotor.

Below is a front view (top) and side view of the motor.

The magnet disks consist of 24 magnets, oriented as radial segments with a magnetization in the direction of the thickness of the disk. These segments occupy 50% of the area of the disk (non-adjacents) and are polarity alternated (N-S magnet, S-N magnet, N-S, S-N, etc). External diameter of the disk is 40 cm; internal diameter is 10 cm. Each magnet segment is 15 cm long.

A 1 Tesla (T) magnetic field can be generated in the air gap of this configuration (2-mm gap for 3 mm magnet thickness) using neodymium rare-earth materials.

The switches need to be able to handle both high current in one scenario and high voltage in the other extreem.
So the semiconductors size and cost go throught the roof, add the IR loss gain for needed worst case voltage needed, making this not feasible quickly.

Has anyone heard of BionX, www.bionx.ca? They make hub motors used in boost systems for bicycles and velomobiles. Their systems go up to 500 watts and are priced around $2,000 with a control system using regenerative braking, http://www.youtube.com/watch?v=eSFE151tRdM. Is the system described here better or cheaper than the BionX system?
I want to mass produce velomobiles with boost systems controlled by I-pads, and could use the help of some smart guys like you.

Readers are directed to two sites:
http://www.technologyreview.com/energy/21666/
http://www.launchpnt.com/portfolio/aerospace/uav-electric-propulsion/
It doesn't look like Exro weathered the recession very well since I haven't seen anything from them lately, but my original analysis of their approach/patent (switched coils to change torque characteristics) led me to believe that the engineering was sound. Likewise for LaunchPoint.

I think you are getting confused between cm and mm. A 10cm(100mm) axil will, depending on what it is made from will easily hand up to 5 x 1.5 tons. I've lifted components up to 30 tons on pins that thick.

Thats kinda scarey, just anyone that knows enough to be dangerous can post all this with the editor of EE times to go ahead and let it happen. I guess thats the downside of this kind of forum. The good side is that someone like roldan speaks up to reprove it, but is he right?

Two years ago "EE Times" reported that "Daimler bus combines hub motors, fuel cells" (http://www.eetimes.com/electronics-news/4197774/Daimler-bus-combines-hub-motors-fuel-cells) so it would appear that the deployment problems for hub motors are not insurmountable. It sounds like one challenge will relate to car handling characteristics having additional mass that will be moving with the wheels (rather than the vehicle body). This is probably less of an issue for a bus. Another design issue will be to ensure that the hub mounted motors are designed to tolerate exposure to the elements near the wheels rather than being protected in the engine compartment.

I would very much like to be a naive high school kid. Unfortunately, I am a retired electronics engineer, with 40 years of background in the industry, acting now as an independent consultant. Almost twenty patents filed. Six presentations at international conferences. One invited paper at ISSCC. My career is behind me.
To be fully honnest, when I tried to patent this concept, I found that this was already done almost twenty years ago. There are at least two naive high school kids dreaming in the world. But, apparently, the other one failed in promoting the concept.
I think, but you can disagree, that it can be very beneficial for the whole industry, and not only the automotive one. For an independent consultant, the automotive industry is too big. I'm more interested in other applications, looking for attractive small niches. But, if I can convince the automotive industry to go in this direction, this should help for developing smaller businesses.
I would enjoy replying to technical questions. In your comment, I can't see any requesting an answer. Please, consider the concept, and not the implementation details.